Phasing system



p 1941- L. A. THOMPSON 2,256,364

PHASING SYSTEM Filed May 16, 1940 INVENTOR. 100/54 T/-/0MPso/v ATTORNEYJPatented Sept. 16, 1941 PHASING SYSTEM Louis A. Thompson, Lakewood,Ohio, assignor to Acme Newspictures, Inc., New York, N. Y., a. a

corporation of Delaware Application May 16, 1940,'erial No. 335,562

14 Claims.

This invention relates to phasing'systems and more particularly to animproved method and circuit'for phasing transmitters and receivers usedin the transmission or'pictures, facsimiles or the like. Although theinvention about to be described will be described in connection with thetransmission of pictures it should be understood that it will haveother. uses, and that the description in the interest of clarity showsmerely one apparatus with which it may be used.

As is well known,. pictures are usually trans-' mitted by means ofapparatus which includes a rotating drum about which the picture issecured. Means for scanning the picture is provided and includes ascanning head which moves longitudinally relative to the drum while thedrum rotates; it has also been proposed to rotate and move the drumaxially simultaneously, withv the scamiin'g head remaining stationary.Al-

' though the system herein described comprises rotating the drum andmoving the scanning head longitudinally of the drum it is not limited inits application to such specific system. The receiver includes a drumabout which a piece of sensitized film is secured and an optical unitwhich is energized by the signal from'the transmitter to expose therotating film in amanner similar to the scanning. The drumson thereceiver and transmitter are operated in synchronism, i.- e., thetransmitter drum operates at exactly the same speed as the receiverdrum. Since both the picture being transmitted and the senentailed onemore operation in the transmission of a picture, making the propositionoi-transsitive film are secured to the drumby clamping means, usually abar extending longitudinallyof the drum, it is necessary that the drumsnot only be kept in synchronism but .that they be in phase; that is, atthe transmitter when the ing a signal which comprises "picture-white"orpicture clamping bar or the meeting edges of the picture are passingthe scanning head, the bar in the receiver or the meeting edges of thefilm should simultaneously be passing the pencilof light from theoptical unit. In other-words,

the transmitter and receiver drums should'be in phase, both clampingbars on the transmitter and receiver, the drums of which are travelingat the same speed (100 R. P. M.), passing by the scanning head andoptical unit respectively simultaneously.

Many means for. causing the phase alignment of the transmitterandreceiver drums have been proposed. Although these means have beenmore or less efiectivethere have been certain inherent disadvantagestherein which it is the purpose of the present invention to overcome.The most the inability to exactly phase the drums; the length of timerequired to eflect such phasing; and also the-fact that thephasingoperation mitting pictures still more diflicult to those nothaving considerable operating experience.

- By the present invention-the phasing is accomplished automaticallywhile the receiving operator is adjusting his machine to the properamplitude for the reproduction of the picture.

That is, the amplitude of the received signal must be amplified to apredetermined value in order that the full range of the different tonevalues of the picture being transmitted are capable'of being recorded.One methodof adjusting the receiver is accomplished by the transmissionof so-called picture-white, i. e., the transmitter is turned on and acertain portion of the drum which is white is scanned and a signalcorresponding to this picture tone, which may be the 1 highest amplitudeis sent out by the transmitter which signal when picked up by thereceiver is amplified and the amplifier controlled to-furnish themaximum amplitude or white that the receiver will be called upon toreproduce. The gainof the receiver and the amplitude of the signal aredetermined by suitable indicators and when once adjusted the receiver isthen ready to reproduce the picture.

In the drawing there has been illustrated diagrammatically that portionof a receiver circuit necessary to accomplish the phasing of picturedrum's according to my invention.

Briefly, the phasing is accomplished by sendmaximum amplitude with aninterrupted period usually obtained at the time the picture clampingbar, which is oflight absorbing character,

passes in front of the optical unit. Fordnstance, with a transmitteroperating at 100 R. P. M. and considering thatthis is the type oftransmitter whereby the picture amplitude is impressed upon 0r mixedwith a carrier wave in order to transmit the same, and assuming that thecarrier frequency is 1800-cycles,'there would be impressed "on the lineor other means of communication the signal to the receiver a series ofsignals comprising 100 pulses per minute;

'each signal including a relatively long 1800 .cycle pulse with a ,4 ofa second interval or no signal (pictures black) between the pulses. The/4 of apparent defects in the prior 'devices'have been 55 .a. secondrepresents the time required for the clamping bar to pass in front ofthe scanning head.

amplified and is used to control an electronic Simultaneously, thereceiver drum amplifier. which is normally operated at the same speed asthe transmitter drum, is provided with means to cause the receiver drumto gradually fall behind the transmitter drum. Means is also providedconnected to the receiver drum and to the previously mentionedelectronic amplifier to also control the amplifier in such a manner thatwhen the control from the transmitter on the amplifier and the controlfrom the local receiver on the amplifier become coincident due to thereceiven drum falling behind the transmitter drum, the power in theamplifier suddenly increases, which increase in power is utilized tooperate a relay which looks out the means for causing the receiver drumto ,fall behind the transmitter and thus places the transmitter andreceiver drums in phase and synchronism.

More specifically, as previously stated, at the start of a transmissionthe transmitting operator transmits picture-white pulses, interruptedfor a duration of approximately ,4 of a second at each revolution of thedrum. This is accomplished by having a zone of white on the edge of thedrum, or the zone of white may be the border of the picture, and byusing a clamp which is black or other light absorbing material to clampthe picture on the drum. The clamp does and as previously stated isdriven by a tuning fork controlled power supply I, the output being 60cycle A. C. at 110 volts. The scanning head 8 I drum. In the receiverand the transmitter the the motor.

not necessarily have to be black throughout its entire length, it needonly be of light absorbing material at the point where picture-white isbeing transmitted for phasing and gain determining l purposes.

It is well known to those in the art that this signal may be effected byfocusing a beam of light on the drum, picking up the light in a.

drums are arranged to rotate while the scanning head traverses the drumlongitudinally by means of the lead screw. l

The negative material is held onto the drum by a clamp I2. The tuningfork power supply is connected to a suitable source of current such as110 volt city current, and the outputfrom the tuning fork is connectedto the receiver through the double-pole double-throw switch indicatedgenerally at l3. When the signal is heard from the transmitting stationthrough a suitable monitor (not shown), the switch is thrown to the onposition. Current flows from the tuning fork power supply through theline I4, through the switch blade l5 to the line l6 and thence to Themotor is a synchronous motor' of a three wire capacitor start type. Thereturn lead H from the motor is connected by the lead Hi to a conductorring 19 disposed on the end of the drum, a suitable brush indicateddiagrammatically by the arrowhead 20 being provided for is preferablyset into a Bakelite base secured to photoelectric or photovoltaic celland using this current to modulate a suitable carrier which for I thepurpose of this explanation will be considered as being generated by an1800 cycle-oscillator. For this particular example the drum of thetransmitter and the receiver both rotate at 100 R. P. M. under thecontrol of tuning fork amplifier power supplies. The clamp for holdingthe picture onto the drum is of sufficient width so that it takesapproximately of a second for it to pass in front of the scanning beam.The operator, therefore, sends out a signal which, because the scanningbeam is scanning picturewhite, is of high amplitude being unmodulatedsince there is but one color and that the amplitude is reduced to zeroor to a sufliciently lower value than the maximum amplitude at the pointwhere the light absorbing bar passes in front of the scanning beam tocause the current differential to accomplish the operation of theinvention. The aforementioned signal is sent to the receiving stationwhere it is taken into' a suitable amplifier and amplified. The figureof the drawing shows the final stage of such an amplifier, the inputbeing,a line I and the ground 2. It should be understood, however,thatthis invention is by no means confined to attachment 6 to the finalstage, as it can be applied in any stage where sufflcient power may betaken from the stage to operate the relay hereinafter mentioned or canbe a separate circuit connected into the receiver atany desired point.

capacitor start type as indicated in the drawing the end of the drum butis not a continuous ring, being broken at one point as indicated at 2|.The space between the broken ends is filled with insulating material sothat the brush rides smoothly as the drum is driven in the directionsindicated by the arrow. A stem or bar I9 is provided for the ringextending radially from the inner edge of the ring to the center, whichbar is connected to the shaft 5, the shaft 5 being grounded as indicatedat 6. The clamping bar l2 for the negative material is disposed on thedrum a predetermined distance in'advance of the gap 2| of the ring.

At this point it should be noted that the motor 4, being a synchronousmotor and -driven by a power supply I closely regulated to give the samefrequency and power output as that of the transmitter motor supply, oncebeing started attempts to travel in synchronism with the motor at thetransmitter, assuming of course that the power supply for bothtransmitter and receiver are so regulated as to give exactly the sametype of output. It should be further noted, however, that the returnlead of the power supply to the receiver motor is through the ring IS,the other lead 23 which connects the motor and extends to the relaycircuit being at this stage open, as shown. The -motor, therefore,having been energized, quickly picks up its speed, but inasmuch as theground return of the motor is through the broken ring l9, when the brush20 reaches the brake 2| the ground return is cutoff and the power supplythus interrupted. The inertia of the drum, however; causes the drum torotate until the brush is again grounded after the gap is moved past thebrush. The motor again immediately picks up speed, obtaining in a partof a revolution its full synchronous speed. The general effect of thisarrangement, however, which comprises a short discontinuance of powersupply'for each revolution of the motor, is to causethe motor and thedrum to fall behind the steadily turning transmitting motor and drum,although at some time does attain ing, the other lead 38 of which isconnected through the coupling coil 36 to the lead '35 at the plates ofthe 6N7 tube. The coupling coil 36 may be the primary of a transformerwhich couples the amplifier to the optical unit or the oscilloscope inthe scanning head 8. This relative large flow of plate current causesthe winding 31 of the relay to be energized, attracts the armaturemaintained continuously, would cause the receiver to keep falling behindthe transmitter until it again comes in phase therewith.

The signal through the line I from the transmitter is fed into a 6N7type tube. This tube is connected as a class -A power amplifier and theelements ar connected in parallelto give greater power output. Thesignal is impressed through the capacity onto the grids of the tubesthrough th lines 26. This signal being a signalof relatively highamplitude and reduced substantially to zero periodically according tothe instant the light absorbing and picture holding bar passes in frontof the scanning beam, drives the grids negative during the highamplitude signal period. By rectification current flows in the gridcircuit from the grid to the cathode, through the cathode resistance 21to ground 2 and from ground 2 through the grid resistance 28 back tothegrid. This causes a relatively large potential drop across the gridresistance 28, because this resistance has a considerably higher valuethan the cathode resistance 21. Thus the grids get a more negative biasand normal plate current will drop from 5 ma. to 3 ma. during thepicture-white period of transmission, returning back to 5 ma. (normalplate current) during the low amplitude pulsations (picture-black) Allthis time the bar I9 of the drum ring is intermittently contacting asecond brush indicated by the arrow 3| and which brush is connected by'the lead 32 through the arm 33 of the relay, indicated generally at 34,and its contact ply to be continuous, plate lead through a resistance 49to ground. An.

points 35 to the cathode lead at l6, shorting out ring at a timeapproaching closer each revolution to the time when the low amplitudesignal is being sent from thetransmitter or the time when no signal isbeing sent. There finally comes a time when there is a lack of signal orwhen the picture-black portion of the signal of low amplitude from thetransmitter is impressed upon the tube grids and the cathode biasresistor is shorted simultaneously by the ring stem IS.

The tube then at this instant has no bias on the .grids and no bias onthefcathodes.

The result is, that this coincident cooperation resulting from theremoval of grid and cathode bias simultaneously causes the platecurrentin the tub to jump to comparatively high value; in the nature of 15 ma.This plate current passes from B+ through the lead 40, switch l3, thelead 39 to the relay 31; thenthrough the relay wind- 42, which hasconnected to it the three movable switch blades. The arm 33 breaks thecontacts at 35 and. the short across the cathode resistor is removed andthe tube is returned to normal operating condition for the purpose ofreceiving the picture. Simultaneously, the arm 43 makes contact at 45and grounds the motor through.

the lead 46, terminating the interrupted power supply to the motor andcausing the power sup- The arm 44 connects the indicator tube isconnected across the resistance 48 and because of this voltage dropacross the resistance 49 the neon tube glows-and indicates that therelay has tripped and that the receiving drum is now in phase with thetransmitting drum. The current passing through the relay and back toground through the contact 44 holds the relay closed.

This operation all occurs in a matter of a fraction of a second. Thatis, at the start of the operation when the operator hears the signal heturns the switch l3 'to the on position, the receiving drum starts,falls into a phase which is indicated by the light and the operator thenadjusts his receiver amplitude to the desired value a as indicated on ameter dial and the receiver is then ready to receive the picture; all ofwhich can be accomplished in approximately ten seconds. Y

It will thus be seen that phasing is accomplished automatically in anexceedingly short space of time. This is of considerable value because,as previously stated, the phasing is exact. The operator does not haveto rely on any'manual operation including the reading of dials to knowwhen the phasing is right, since it automatically is taken care of.Inasmuch as only such a short time is necessary, it reduces the amountof time for transmission, which is of considerable importance whentransmissions are being handled over long. distances, resulting in anobvious economy.

After transmission the ofi-on switchis thrown to the oil? position,which releases the relay and terminates the tuning fork power supply ina load resistanc equal to the impedance of the motor, thus preventing anabnormal open circuit condition in the power supply, and preparing themachine for subsequent receptions.

Although I have described my invention in a specific embodiment thereof,1 am aware that numerous and extensive departures may be made therefromby those skilled inthe art, but without departing from the scopeorspirit of the invention. The invention, therefore, is not to be limitedto the specific embodiment shown, the

limitations merely being delineated by the accompanying claims.

I claim:

1. The; method of synchronizing and phasing two rotating members whichcomprises driving said members at a synchronous speed, using one of saidmembers to generate a phasing signal and control a thermionic circuitthereby, interrupting the drive or said other member to cause saidmember to shift its phase relationrelative to the first and using saidsecond rotating member to provide additional periodic control eachrevolution for said thermionic circuit, and looking out said interrupteddrive with said thermionic circuit when a predetermined phaserelationship between the rotating members is established.

2. The method of phasing the drums of telephoto transmitters andreceivers, which comprises generating a voltage at the transmitter whichvaries in amplitude for a portion of each cycle at a predeterminedposition of the drum, using the receiver drum to control an amplifyingcircuit and using said generated voltage to exercise additional controlon said circuit and causing said receiver drum to fall behind thetransmitter drum and using the output of said amplifier circuit when thereceiver control and received voltage become coincident to lock saidreceiver drum in phase with the transmitter.

3. The method of phasing the drums of telephoto transmitters andreceivers, which comprises generating a signal at the -transmitter whichvaries in amplitude fora portion of each cycle at a predeterminedposition of the drum, and applying said signal to the grid circuit. of avacuum'tube amplifier at the receiver, using the receiver drum tocontrol the cathode circuit of said amplifier, interrupting the powersupply tosaid receiver drum to cause said receiver drum to fall behindthe transmitter drum and using the output of said amplifier circuit whenthe receiver controland receivedvoltage become coincident to lock saidreceiver drum in phase with the transmitter.

4. The method of phasing the drums on telephoto transmitters andreceivers which comprises generating a signal at the transmitter .whichis interrupted in accordance with the position of the drum relative tothe point of scanning, driving the drum at the receiver in synchronismwith the transmitterrand interrupting the drive. of the receiver drumtocause the re-- ceiverdrum to fall behind thetransmitter drum* drivingcircuits when a predetermined phase re-- lation is established betweenthe transmitter and the receiver. l

5. The method of phasing telephoto transmitters and receivers whichcomprises generating a signal in the transmitter of high. volume andchanging the amplitude of said signal at a irequency dependent on thedrum speed, receiving said circuit; said other rotating member havingplate current to remove said retarding mean for said second member.

7. A phasing system for the drums of telephoto receivers andtransmitters which includes means connected to the transmitter forgenerating a voltage which varies in amplitude in timed relation to therotating drum, a thermionic amplifier electrically connected to saidtransmitter and including a plate circuit, a grid circuit and a cathodecircuit, said transmitter signal being coupled to the grid circuit of anamplifier and operative to control the grid bias in said circuit whichin turn controls the plate current fiowing in the amplifier; said otherreceiving drum having means tointerrupt the drum drive each revolutionof the drum to cause a periodic phase shift of the drum relative to thetransmitter drum; means operated by said receiving drum and connected tosaid amplifier to change the cathode circuit bias in timed relation tothe rotation of the receiving drum, and relay means in the plate circuitof the amplifier operable upon a predetermined rise in plate current dueto coincident operation of the grid and cathode bias-controlling meansto remove said interrupted receiver drum drive and cause said drive tobe uninterrupted. s

8. A telephoto transmitter and receiver phasing system comprising meansat the transmitter -for generating a constant signal of maximum value tobe transmitted interrupted at one point per each revolution of thetransmitter drum to reduce the signal to a lower amplitude, means forreceiving the signal at the receiver, and amplifying the signal to ahigher amplitude than "that normally used for recording .the picture,

said receiver including a receiving drum, and

T drive means to rotate the receiver drum in synsaid signal at. thereceiver; driving said receiver 7 at a speed nearly that of thetransmitter by interrupting the drive for part of the time, causing thetransmitted signal and the interrupted receiver drive to control theoperation of an electron amplifier using the output of said amplifier tolock said receiver and transmitter into step when the receiver fallsbehind the transmitter to the point where the interruption in thereceived signal coincides with the interruption in the receiver drive.

-cuit, a grid circuit and a cathode circuit; said signal-being fed intothegrid circuit of an amplifier and operable to control the grid bias inchronism with the transmitting drum,-means connected .to said receiverdrum drive means to interrupt said driving means for a portion of therevolution of the drum to cause said receiving drum to change its phaserelation with the transmitting drum, circuit means connected to andoperable by the receiving drum to control the'operation of an electronicamplifier, said amplifier also being controlled by said received signal,a relay connected to said amplifier output and operable upon apredetermined increase in current in the. amplifier due to coincidentoperation of the control means for the amplifier to lock said receiverin phase with the transmitter.

9. In combination with a picture transmitter and receiver each having asynchronously driven drum and a scanning head, the transmitter havingmeans to transmit a high amplitude signal which is varied in amplitudeat the time when the meeting edges of the picture pass by the scanninghead, retarding means for the receiver to cause the receiving drum tofall behind the transmitting drum, electronic means for disengaging saidretarding means for the receiving drum,, including an electronicamplifier, said transmitted signal. connected to saidFamplifier, andmeans connected to the receiving drum and operable when the meetingedges of the film pass in front of the scanning head and connected tosaid electronic amplifier, saidsignals from the transmitter and receiverco-acting in said electronic amplifier when the edges of the films in gthe transmitter and receiver pass in front of the light source and alens system for directing a pencil of light on said picture and aphoto-electric responsive means for picking up said reflected light fromsaid picture, a synchronous motor for rotating said drum at apredetermined speed and a source of power supply for said mtor, saidclamp in the end zone of the drum being provided with alight absorbingsurface, and said drum being provided with a light reflecting surface inthe end zone, and means to amplify said signal from the photo responsivemeans and direct said signal to a point remote from the receiver, saidsignal upon operation of said transmitter and scanning said end zone,constituting a signal of high amplitude interrupted by a space ofdifierent amplitude when said clamping bar passes in front of saidpencil of light, a receiver for receiving said transmitted signal andin- -cluding an amplifier for amplifying said signal,

a receiving drum for holding and rotating a light sensitive film and asynchronous motor for'driving said drum at exactly the same speed as thetransmitter, a power supply for said motor and connected to said motorthrough a stationary brush and a contact ring on the drum, said contactring being broken at one point to cause said motor circuit to be brokenduring each revolution of the drum and operable to cause said receivingdrum to fall behind said transmitting drum a part of a turn during each.revolution of said drums, means to establish an unbroken current supplyto said receiving drum when a predetermined phase relation between thesaid drums is establishedcomprising a vacuum tube circuit and a relaydisposed in the output thereof, said signal from the transmitter beingconducted to the grid circuit of said vacuum tube and operable tomaintain a high grid bias during the high amplitude periods of thesignal and maintain a lower than normal plate current and to lower thegrid bias during the low amplitude signal periods, means on saidreceiving drum connected to said vacuum tube circuit to intermittentlyreduce the cathode bias on said tube, the timed relation of the re movalof bias from said grid and cathode circuits of the vacuum tube circuitvarying with the phase relation of said drums, said plate current insaid tube circuit increasing to a high value when the 1 bias on the gridand cathode circuit occur simultaneously,said high plate current adaptedto operate said relay and said relay adapted to lock out saidinterrupted current supply for the receiving drum and hold said relayclosed with ing drum to shift its phase relation to thetransmittingdrum, means to shunt out said commutator connection for thereceiving drum and supply uninterrupted power supply therefor comprisinga shunt. controlling relay, and means to operate said relay when thereceiving and-transmitting drums are in phase comprising an amplifierincluding a thermionic tube, said relay being disposed in the outputcircuit of the tube, and control means on the transmitter and receiveroperable in timed relation to said drums to control the output of thetube.

12. An transmitter and a receiver, each including a scanning head and a.picture drum adapted to have a picture clamped thereon, synchronousmotors for. each of said drums for rotating them in synchronism, saidmotor circuit for the receiving drum being connected through acommutator on the drum to interrupt the power supply to the motor onceeach revolution to cause said receiving drum to shift its phase relationto the transmitting drum, means to shunt out said commutator connectionfor the receiving drum and supply uninterrupted power supply thereforcomprising a shunt controlling relay, and means to operate said relaywhen the receiving and transmitting drums are in phase comprising anamplifier'including a thermionic tube, said relay being disposed in theoutput circuit of the tube, and control means on the transmitter andreceiver operable in timed relation to said drums to control the .outputof the tube,.said control means adapted to control the grid and cathodebias respectively of the tube and operable upon predetermined coincidentcontrol to increase the plate current sufliciently to operate the relay.

13. A picture transmission system, including a transmitter having a drumfor holding a picture to be transmitted, means on the drum and holdingthe edges of the picture, a scanning system i for scanning the picture,photo electric responsive means for picking up said reflected light fromsaid picture, a motor for rotating said drum at a predetermined speed,and means to amplify said signal from the photo responsive means anddirects said signal to a point remote from the receiver, said signalupon operation of said transmitter constituting a signal of highamplitude interrupted by a space 'of difl'erent amplitude, a receiverfor receiving said transmitted signal, a receiving drum for holding androtating a light sensitive film anda motor for driving said drum at thesame speed :as the transmitter, a power supply for said motor andconnected to said motor through. a contact ring on the drum, saidcontact ring being broken at one point to cause said motor circuit to bebroken during each revolution of the drum to cause said receiving drumto fall behind said transmitting drum a part of a turn during eachrevolution of said drums, means able to maintain a high grid bias duringthe high amplitude periods of the signal and maintain a lower thannormal plate current and to lower the grid bias during the low amplitudesignal periods,

means on said receiving drum connected to said vacuum tube circuit tointermittently reduce the cathode bias on said tube, the timed relationof the removal'of bias from said grid and cathode circuits of thevacuum-tube circuit varying with the phase relation of said drums, saidplate current in said tube circuit increasing to a. high value when thebias on the grid and cathode circuit occur simultaneously and adapted tooperate said relay and said relay adapted to lock out said interruptedcurrent supply for the receiving drum and hold said relay closed withsaid drums v A in phase with each other.

14. The method of synchronizing and phasing two rotating members whichcomprises driving said members at synchronous speeds, shifting the phaserelationship between the two members by interrupting the drive of one ofsaid members 10 rotating members is established.

LOUIS A. THOMPSON.

